Multidimensional scaling and factor analysis of tantrum descriptions provided by parents indicate that tantrums consist of two main sets of behaviors. Anger-related behaviors, e.g., shouting, hitting, kicking, stamping, or throwing, are maximal at tantrum onset and decline within a few minutes. Whining, comfort-seeking, and crying are distress-signalling behaviors. Crying occurs with a probability of about 50 percent at tantrum onset and increases in probability and intensity throughout the tantrum; comfort-seeking increases sharply toward the end. Further evidence for the separability of anger and distress comes from our study of right/left hemisphere EEG asymmetries in tantrum prone and non tantrum prone 4 year olds in which there was a significant correlation of right frontal cortex activation with facial expressions of sadness while left posterior temporal activation was associated with both parental reports and laboratory measures of anger. Although independent, anger and distress overlap in the tantrums of most children. With clinical psychopathology, however, tantrum patterns may become exaggerated in one or another direction. Several lines of evidence suggest that 4 year olds presenting primarily with externalizing behavior disorders may have frequent, predominantly angry tantrums in which they are more likely to run away than throw themselves down. Four year olds with primarily internalizing emotional disorders may have prolonged, predominantly distress related tantrums in which they are more likely to seek comfort and/or throw themselves down than run away. We propose to test this hypothesis by training parents of externalizing and internalizing 4 year olds to record their children's tantrums. We propose to determine if tantrum characteristics predict the reactions of these children to emotion eliciting situations in the laboratory. Some physiological indices suggest that baseline levels of physiological arousal and stress are lower in externalizing children and higher in internalizing children. We propose to test the hypotheses that skin conductance baseline levels and reactivity may be inversely associated with tantrum anger while salivary cortisol baseline levels and reactivity may be directly related to tantrum distress. Children typically relinquish tantrums by their fifth year, studies have shown that tantrums persisting to age 8 are strongly prognostic of poor adjustment. We propose to extend this to a younger age by testing whether the frequency, duration, or behavioral content (anger and/or distress) of tantrums at 4 years of age predict the persistence of tantrums and the severity of psychopathology at 5 years.